The present invention relates to an iron head for an iron type golf club. More particularly, the present invention relates to an iron head having a hollow portion.
An iron type golf club includes a shaft and an iron head disposed at a distal end of the shaft, so that a striking face of the iron head hits a ball. The shaft is inserted and fixed into a hosel formed in the iron head. A side of the iron head where the hosel is formed is referred to as a heel, and an opposite side of the iron head, i.e., a distal end side thereof, is referred as a toe. A bottom side of the iron head facing a ground surface is referred to as a sole. A plurality of grooves, i.e., score lines, is formed in the striking face of the iron head with a certain distance therebetween in a vertical direction.
Patent Reference 1 has disclosed a conventional iron head. The conventional iron head has a recess portion disposed at an upper portion of a back surface thereof, and a hollow portion is disposed behind the striking face below the recess portion. With the hollow portion formed in the iron head, it is possible to lower the center of gravity of the iron head. Further, the center of gravity is shifted backward from the striking face of the iron head, thereby expanding a sweet area thereof. In addition, when the hollow portion is formed in the iron head, a weight of the iron head is reduced. Therefore it is possible to increase a size of the iron head without increasing the weight thereof. Further, when a weight distribution increases on the toe side and the heel side of the iron head, it is possible to increase the sweet area of the iron head without increasing the weight thereof.
In Patent Reference 1, the conventional iron head has the hollow portion extending from the proximity of the toe to the proximity of the heel. A thickness of a face plate, or a distance between the striking face and the hollow portion, is substantially uniform between the toe side and the heel side.
Patent Reference 2 has disclosed another type of conventional iron heads. The conventional iron head has a hollow portion disposed behind a striking face, and a shock absorber made of a rubber, urethane, or silicone is disposed in the hollow portion. The shock absorber has a thickness about 1.5 mm to 8.0 mm.
Patent Reference 3 has disclosed a golf club having a striking face capable of bending like a wood club. With the configuration, it is possible to hit a ball for a long distance.
Patent Reference 4 has disclosed an iron head having a hollow portion and a viscoelastic body disposed in the hollow portion. The viscoelastic body enables to dampen a vibration of the iron head.
Patent Reference 5 has disclosed an iron head including a cavity portion in an upper portion of a backside surface thereof and a protruding portion in a lower portion of the backside surface thereof. The iron head further includes a hollow portion being concaved toward a sole surface side in an upper portion of the protruding portion. In Patent Reference 5, the iron head includes the hollow portions disposed in both of a heel side and a toe side thereof.    Patent Reference 1: Japanese Patent Publication No. 2000-210400    Patent Reference 2: Japanese Patent Publication No. 09-117537    Patent Reference 3: U.S. Pat. No. 4,398,965    Patent Reference 4: Japanese Patent Publication No. 06-319836    Patent Reference 5: Japanese Patent Publication No. 2010-017475
In the conventional iron head disclosed in Patent Reference 1, the thickness of the face plate between the striking face and the hollow portion, in other words, the distance between the striking face and the hollow portion, is substantially uniform in a toe to heel direction. When the golf club having the iron head hits a ball at a middle portion thereof, it is difficult to obtain a strong impact feeling due to the hollow portion formed behind the middle portion and the small thickness of the face plate at the middle portion of the iron head.
In view of the problems described above, an object of the present invention is to provide an iron head having a wide sweet area and capable of obtaining a strong impact feeling when hitting a ball at a middle portion thereof.